5 - Leak detection
Never use oxygen or dry air in order to avoid the
risk of fire or explosion.
• Perform a leak detection test on the complete
system by means of: a dry nitrogen pressure test,
a mixture of nitrogen and the refrigerant to be
used in the system, a helium leak test and/or a
deep vacuum test.
• The test should be long enough in duration to
ensure the absence of any slow leaks in the system.
• Use tools specifically designed for detecting leaks.
• The low side test pressure must not exceed
1.1 x Ps pressure indicated on the compressor
nameplate.
• For high side test pressure, do not exceed
the pressure indicated on the condensing unit
nameplate.
• Whenever the condensing unit is equipped with
suction and liquid shut-off valves, these valves are
to remain in the closed position while performing
the leak test (condensing unit leak test already
performed in the factory).
• Should a leak be discovered, proceed with
repair steps and repeat the leak detection.
• When a deep vacuum leak detection test is
selected, observe the following:
1) The level to reach is 500 µm Hg.
2) Wait 30 min.
3) If pressure increases rapidly, the system is not
airtight. Locate and repair leaks. Restart the
vacuum procedure, followed by steps 1, 2, etc.
4) If pressure increases slowly, the system contains
moisture inside. Break the vacuum with nitrogen
gas and restart the vacuum procedure, followed
by steps 1, 2, etc.
5) Connect the compressor to the system by
opening the valves.
6) Repeat the vacuum procedure, followed by
steps 1, 2, etc.
7) Break the vacuum with nitrogen gas.
8) Repeat the vacuum procedure, steps 1, 2;
a vacuum of 500 µm Hg (0.67 mbar) should be
reached and maintained for 4 hours. This pressure
is to be measured in the refrigeration system, and
not at the vacuum pump gauge.
Do not use a megohmeter or apply power
to the compressor while it is under vacuum, as
this may cause motor winding damage (motor
burn-out).
Do not use colored leak detection fluids. Do
not use chlorofluorocarbon in leak testing systems
designed for HFC fluids.
6 - Vacuum dehydration procedure
Whenever possible (if shut-off valves are present),
the condensing unit must be isolated from the circuit.
It is essential to connect the vacuum pump to both
the LP & HP sides, in order to avoid dead-ending
system parts.
Recommended procedure:
1) Once leak detection has been completed,
2) Pull down the system under a vacuum of 500 µm
Hg (0.67 mbar).
3) When the vacuum level of 500 µm Hg has been
reached, the system must be isolated from the
pump.
4) A vacuum of 500 µm Hg (0.67 mbar) has to be
reached and maintained for 4 hours. This pressure
is to be measured in the refrigeration system, and
not at the vacuum pump gauge.
If pressure increases, restart the leak-detection
procedure (refer to the «
Leak detection
» section
of this manual if necessary).
Vacuum pump:
A two-stage vacuum pump with gas ballast valve
(0,04-mbar standing vacuum) shall be used; its
capacity is to be consistent with system volume.
Never use the compressor as a vacuum pump. It
is recommended to use large-diameter connection
lines and to connect these lines to the shut-off
valves, rather than to the Schrader connection.
This recommendation allows avoiding excessive
pressure losses.
Moisture level:
At the time of commissioning, system moisture
content may be as high as 100 ppm. During
operation, the liquid line filter dryer must reduce
this level to < 20 ppm.
Additional notes:
• To improve moisture removal, the temperature
of the system should not be lower than 10°C.
• A proper vacuum procedure is even more
important with HFC and polyolester lubricant than
it has “traditionally” been with HCFC (R22) or
CFC and mineral oil.
• For further details, please refer to TI 3-026.
Do not use a megohmeter or apply power to
the compressor while it is under vacuum, as this may
cause motor winding damage (motor burn-out).
7 - Electrical connections
• Make sure the main power supply to the system
has been switched off and isolated, in accordance
with applicable regulations, before performing
any electrical connection.
• Please refer to Figs 5 and 6 for typical wiring
connections and examine the specific wiring
diagram located in the electrical box cover.
For further details, refer to the condensing unit
guidelines.
• Note that Maneurop
®
compressors fitted on
condensing units are protected against overheating
and overloading by an internal safety motor
protector. However, an external manual reset
overload is recommended for protecting the circuit
against over-current.
• The “must trip” value of this overload relay must
be set in accordance with power line sizing and
design and shall never exceed the “A max.” value
stamped on the nameplate.
• On units equipped with an electrical box, all
electrical connections (condenser fan motor,
compressor motor, pressure control switch,
crankcase heater, etc.) have already been wired
at the factory. For single-phase compressors,
start-and-run capacitors are included in the
connecting box.
• The connecting box is equipped with screw type
terminal blocks, for both power and control lines as
well as earth terminals for grounding connections.
• All electrical components must be selected as
per local standards and condensing unit component
requirements.
8 - Filling the system
• Before charging the refrigerant, verify that the oil
level is between 1/4 and 3/4 on the compressor
oil sight glass and/or ensure that the oil charge of
the original compressor is sufficient as regards
system dimension and piping design:
- An additional quantity of oil might be necessary
for line lengths (back and forth) in excess of 20 m.
- In the event additional oil is required, use only an
approved lubricant (refer to the «
Introduction
»
section of this manual).
• Make sure the refrigerant used to fill the system
is compatible with compressor design. Refer to
the «
Introduction
» section of this manual for an
approved list of refrigerants.
• Compressor switched off: the liquid refrigerant is
charged into the condenser and/or liquid receiver
in the liquid phase (compulsory for refrigerant
blends). The charge must be asclose to the nominal
system charge as possible in order to avoid both low
pressure operations and excessive superheating
at start-up. Throughout this operation, both
compressor service valves must remain closed.
• Remember that vapor-charging is only appropriate
for pure refrigerants, such as R22.
• To the extent possible, maintain the refrigerant
charge below 2.5 kg per cylinder. Above this limit,
install a system, such as a pump-down cycle or
suction line accumulator, to prevent against liquid
flood-back into the compressor.
• Be sure that the refrigerant charge is suitable for
both winter and summer operations.
9 - Verification before commissioning
Ensure that all service valves are in the open
position before start-up. A closed discharge or
suction service valve may cause serious damage to
the compressor and/or compromise safety device
operation, thereby resulting in potential injury to
personnel.
• Check that all safety devices are operational and
properly set (safety pressure switch set point,
mechanical relief valve if necessary, etc.). Make
sure that these devices comply with both
generally - and locally - applicable regulations
and standards (e.g. EN378).
• When using high-pressure switches or relief
valves, the setting must not exceed maximum
service pressure of any system component. Refer
to the Application Guidelines for relevant condensing
unit pressure safety limits.
• A low-pressure switch is recommended to
prevent operation under vacuum. Use a minimum
setting of 1.2 bar (absolute).
• Verify that all electrical connections are properly
fastened and in compliance with local safety
regulations.
• A compressor crankcase heater is factory
installed, ensure that it has been energized for a
minimum of 12 hours before initial start-up and/or
during prolonged shutdown periods.
10 - Start up
Never start the compressor in the absence of
a refrigerant charge.
• Do not bypass the LP or any other safety
switches during start-up
• Check current draw and voltage levels.
• Monitor the oil sight glass to ensure proper oil return
to the compressor. After 2 to 4 hours of operations
under established conditions, check the oil level
and add oil if necessary (refer to TI bulletin 3-025).
Instructions
5
8510198 P03-A © Danfoss Commercial Compressors 03/05
